This invention relates generally to the field of devices for the destruction, encapsulation or disposal of potentially hazardous plastic waste, especially such waste comprising used medical syringes with attached needles or lancets. More particularly, the invention relates to such devices which melt and compact the plastic waste to completely encapsulate the needles into a sterile, disposable slug.
It is necessary to dispose of used medical syringes, lancets and blood test strips in a manner which minimizes the possibility of injury or infection to persons handling the syringes, at the initial point of use and disposal as well as all along the handling chain to final disposition in a land fill or the like. Numerous methods or devices have been developed to address this problem. Some such devices provide means to cap or enclose the needle, but enclosure of the needle by a physical housing requires the person to perform an additional physical act where inadvertent contact is possible and does not address the need to sterilize the syringes to kill infectious organisms. Devices are also known which provide protection from the syringe needles by melting the plastic portions of the syringes such that the needles are encased in the resulting plastic mass. This technique is an improvement over the capping method, since the used needle is simply deposited into the disposal device with minimal handling. The temperature achieved within the melt chambers of these devices is greater than that required to melt the plastic in order to also sterilize the waste material.
Examples of such combination disposal and sterilization devices are shown in U.S. Pat. No. 4,800,958 to Yerman and in U.S. Pat. No. 5,207,994 to Suziki. These devices provide a cylindrical melting chamber with a reciprocating piston. The waste syringes are placed into the chamber, heated and compressed to form a puck or slug to encapsulate the needles. The plastic slug is then removed by opening separate access plates or doorways and disposed of.
Both of these devices, as well as all other similar known devices, involve multiple joints, doorways, hinges and other components which are susceptible to fouling from plastic flash. Plastic flash is molten plastic which escapes from the melting chamber due to the effects of gravity or pressure from the compacting piston. Syringe plastic contains paraffin, which becomes a highly viscous liquid at temperatures well below those required to sterilize the plastic waste. The sterilization step requires temperatures in excess of 350 degrees F. to achieve sterilization in a relatively short time period. During the melting process, at about 275 degrees F., the paraffin becomes a highly viscous liquid which is forced past the seals and joints in the known devices. To counter this, highly efficient seals and joints must be constructed with very tight precision. These air and fluid tight seals prevent the escape of water vapor, steam and other outgas products produced during the melting process. Since they cannot escape and are non-compressible, they recondense on or within the waste slug and create gaps and voids within the slug through which the needle points may be exposed.
It is an object of this invention to provide a device for the destruction, sterilization and encapsulation of hazardous plastic waste products, and in particular waste such as used medical syringes with attached needles, lancets, blood test strips or the like, which provides a safe and efficient means to form the plastic waste into a disposable plastic slug with the needles securely encased therein by combination of pressure and temperature. It is a further object to provide such a device which allows gas and liquids to escape from the melting chamber such that they are not retained within the waste slug. It is a further object to provide such a device which eliminates the problems associated with plastic flash by providing a melting chamber machined from a single block or cast to have no joints or seams, and which reduces the number of joints, seals and moving components required to accomplish the task in order to simplify the device. It is a further object to provide such a device in which a reciprocating compaction head for the plastic waste is constructed such that the waste slug becomes temporarily attached to the compaction head such that the plastic slug is removed from the melt chamber by retraction of the compaction head. It is a further object to provide such a device in which the compaction head is reciprocated by a rotating cam and in which the plastic slug is at least partially ejected from the compaction head by a second rotating cam.